Suspension bridge framework

Abstract

Framework for a suspension bridge of the type comprising an essentially flat main structure, the top surface of which forms the traffic lane for the transport structure crossing the bridge, anchored to a suspension system formed of a plurality of vertical hangers (6) fixed to catenary cables (5) anchored to end piers of the bridge. The framework consists of at least two parallel longitudinal box-like bodies corresponding to two runways of the bridge, reciprocally spaced by an extent equal to their transverse dimension. Said bodies have a cross section with a profile adapted to favor the proper flow of the wind stream and they are interconnected, at regular intervals, by stiff supporting transverse ledgers (4) having in turn a box-like configuration and carrying at their ends means for their anchorage to the suspension hangers (6).

I claim: 
     
       1. A suspension bridge having a framework comprising a substantially flat main structure, said main structure having a top surface which forms a traffic flow lane, a suspension system formed by a plurality of vertical stays or hangers (6) fixed to catenary cables (5) anchored to end piers of the bridge, said framework being anchored to said suspension system, said framework comprising a plurality of parallel box bodies extending longitudinally of the bridge and corresponding to two runways of the bridge, said box bodies being spaced apart a distance equal to their transverse dimension, and stiff supporting transverse ledgers (4) by which said box bodies are interconnected at regular intervals, said box bodies having a transverse cross section which is an aerodynamic profile. 
     
     
       2. A suspension bridge as claimed in claim 1, wherein said longitudinal box bodies have upper surfaces that are flat and under surfaces that are curved with a profile to favor flow of a wind stream. 
     
     
       3. A suspension bridge as claimed in claim 1, wherein securement of the framework to suspension hangers (6) is provided only at the ends of said ledgers. 
     
     
       4. A suspension bridge as claimed in claim 1, having thereon gratings forming safety runways positioned in free spaces between the longitudinal box bodies. 
     
     
       5. A suspension bridge a claimed in claim 4, wherein said gratings have a transparency of the order of 70% so as to let through a wind stream. 
     
     
       6. A suspension bridge as claimed in claim 1, wherein said longitudinal box bodies have dimensions to accommodate people along their length. 
     
     
       7. A suspension bridge as claimed in claim 1, wherein said ledgers have a box configuration. 
     
     
       8. A suspension bridge as claimed in claim 7, wherein said ledgers have dimensions to accommodate people along their length. 
     
     
       9. A suspension bridge as claimed in claim 1, wherein said longitudinal box bodies engage in vertical walls of said ledgers, manholes being provided in said walls to allow people to pass from said bodies into the ledgers and vice versa. 
     
     
       10. A suspension bridge as claimed in claim 1, comprising three parallel longitudinal box bodies, a central body carrying railway lines, and two lateral bodies carrying roadway traffic.